The deactivation effects of Nd3+ ion for 2.85 μm laser in Ho3+/Nd3+ co-doped fluorotellurite glass

The 2.85 μm band has garnered significant attention for its wide range of applications in the mid-infrared region, and Ho³⁺ doped fluorotellurite fiber shows great promise as a gain medium for the 2.85 μm fiber laser. To achieve efficient population inversion for Ho³⁺ ions at 2.85 μm, Ho³⁺/Nd³⁺ co-doped fluorotellurite glasses with low hydroxyl were synthesized. The deactivation effect of Nd³⁺ ions to Ho³⁺: ⁵I₇ levels was investigated through emission spectra and lifetime decay curves under 890 nm excitation. The results show that Nd³⁺ ions can effectively quench the Ho³⁺: 2.05 μm emission and help the Ho³⁺: ⁵I₆ → ⁵I₇ transition to overcome the bottleneck of particle population inversion. Ultimately, the particle population inversion corresponding to 2.85 μm luminescence was realized in the Ho³⁺/Nd³⁺ co-doped fluorotellurite glass, and indicates that a maximum of 1.64 W laser at 2.85 μm with a slope efficiency of 8.72 % can be realized under 890 nm pump by numerical simulations.